For starters---the movie should have been named 'The woman on the train' instead of 'girl' , for Emily Blunt is obviously not shown young enough to be called a 'girl' . But the moviemakers probably wanted the movie to appeal to a younger audience .

Emily plays a woman who thinks that her marriage has collapsed because of her drunkenness and the blackouts that occur because of it , and also because she can't conceive a child . She sometimes stalks her ex husband and his new wife and child , taking the baby in her arms one day until his wife forces her to lay it down . Emily no longer goes to her job and her obsession is to travel to and fro by the same train everyday . The train passes by her ex husband's neighbourhood and she can see his family . Also she develops an addiction to watch a beautiful blonde girl and her husband romancing on their house's balcony many times while watching through the train .

But one day Emily sees the girl kissing another man on the same balcony and she is deeply disturbed by the sight of the perfect romantic marriage breaking down . After a drinking binge , she decides to go and confront the girl and call her a whore , but has a blackout as she goes to confront and does not remember what she saw . Later she comes to know that the girl has disappeared....

So what could have happened ? Did the girl just run off with her new lover ? Or was she murdered---but by whom ? The psychiatrist whom she was regularly visiting and on whom she was trying to hit on ? Her husband in a fit of jealousy ? Or did Emily herself murder her but did not remember later due to her blackout ? Watch the movie for the answers .

The movie rests on the acting capabilities of Emily Blunt , and she carries it off with aplomb . Her acting of a person who is unstable due to heavy drinking is perfect ; the voice and expressions and her own anguish at her condition has been thoroughly well acted out . Other actors act well too . Photography is okay and background music is appropriate for the situations .

But even though I have not read the novel on which the movie is based , I could sense that it is not as great as the novel . Of course , except on one point the novel is copied faithfully in the movie according to what I heard . But I was not fully convinced when the mystery was solved . The person who did what he/she did on a reason that does not fully qualify as a valid reason for doing that ; many people would let things solve themselves out if confronted with the same situation . The situation was not extreme enough to warrant taking the step that person did . Or so I thought , for others who see the movie might disagree....